Retries & Error Handling
The documentation on the deprecated Neo4j Streams plugin and the previous version of the Kafka Connect Neo4j Connector can be found here.
Messages being processed by Kafka Connect Neo4j Connector may provoke transaction errors in Neo4j. In general, Kafka Connect Neo4j Connector does not support retries, and careful thought is needed to design a strategy that will work. For example:
Errors may be caused by too much parallelism and node locking when writing relationships; in this case, rather than retries, a different write mechanism is a better idea
If Kafka Connect Neo4j Connector grows to support retries, it needs to have configurable strategies for how many times to retry, when to backoff, and so on. This would greatly complicate the situation
If a cascade of errors starts happening (for example during a leader re-election) under constant load from Kafka, you could have a cascade of retries, which would basically turn into a denial of service attack on the cluster.
For all of these reasons, Kafka Connect Neo4j Connector doesn’t support retries but sends error messages (at the user’s option) to a configurable dead letter queue. (DLQ). If your application needs retry logic you might consider downstream logic on the DLQ to handle them however is appropriate.
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